This invention relates to auxiliary fuel systems and, in particular, to a mounting system for a crash worthy, auxiliary fuel system for a helicopter.
Auxiliary fuel tanks have long been used to extend the range of a helicopter and other aircraft or to provide refueling capability at a remote location. Depending upon the size and type of helicopter, auxiliary fuel tanks have been located in pods outside the helicopter, under seats, in cargo bays, and elsewhere. For some applications, e.g. surveillance or patrol, an added fuel tank may be an essentially permanent installation. For rescue or other operations, it is desirable that an auxiliary fuel tank be easily installed or removed in order to re-configure a helicopter as quickly as possible; e.g. in ten minutes or less.
A problem with many of these installations is that the system is not crash worthy. As used herein, a "crash worthy" fuel system is one that will not leak fuel when subjected to an impact that human passengers are likely to survive. Although there are many variables that affect the severity of an impact, the abrupt application of a force in excess of twenty "g's" (twenty times the force of gravity) is generally considered the upper limit of a survivable crash.
The conflicting requirements of crash worthiness and ease of installation or removal are difficult to meet simultaneously, particularly when the fuel tank is large, e.g. holding one hundred ninety-five gallons of fuel (thirteen hundred pounds) or more. Ease and speed of installation or removal implies that there are relatively few parts, that the parts are easily handled by male or female personnel, and that installation or removal requires no tools. Not requiring any tools is especially important if the fuel tanks are removed or installed in remote locations, rather than at a local airport.
In order for a fuel tank to be crash worthy, fuel must be contained in such a way that stress is distributed as uniformly as possible over the surface of the fuel tank. A crash worthy fuel tank includes a crash worthy bladder within a resilient fiberglass case. During impact, the bladder and case may distort but do not fail. Fasteners attached directly to the case are not practical because of the localized stress imposed by the fasteners. Fuel line fittings include break-away, self-sealing connectors to avoid imposing a breaking stress on the fuel line during a crash.
In general, a crash worthy fuel tank contains the fuel. What is needed is a mounting system for containing the tank in such a way that the combination is crash worthy. Preferably, the system for mounting the fuel tank does not require significant modification of the helicopter, which could complicate the installation of other equipment, such as seats, stretchers, and the like, when an auxiliary fuel tank is not installed.
In view of the foregoing, it is therefore an object of the invention to provide a crash worthy mounting system for an auxiliary fuel tank in a helicopter.
Another object of the invention is to provide a mounting system for an auxiliary fuel tank that does not require modification of the helicopter for installation.
A further object of the invention is to provide a mounting system for an auxiliary fuel tank that does not require extensive modification of the fuel tank.
Another object of the invention is to provide a mounting system for an auxiliary fuel tank that enables the tank to be installed or removed quickly and without the use of tools.